IT202100003458A1 - SYSTEM AND METHOD FOR VIBRATION REDUCTION IN PRESSURE SWING SYSTEMS - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

?SYSTEM AND METHOD FOR VIBRATION REDUCTION IN PRESSURE OSCILLATION SYSTEMS?

Technical field

The present invention relates to the field of systems which produce vibrations, such as for example cryogenic systems, or cryo-refrigerators, which include means for producing pressure oscillations (e.g.: rotary valves or pistons or displacers), and in particular refers to cryo-coolers without cryogenic liquids, also called ?cryogen-free? or ?dry?, in a closed cycle. Pi? specifically, the present invention relates to a device and a method for stabilizing and suppressing the vibrational noise induced by the simultaneous operation of at least two of the aforementioned means which produce pressure oscillations, such as, for example, the rotary valves present in pulsed tube cryo-coolers ( PTC) of the Gifford-McMahon type, for applications that need to operate in cryogenic environments with high cooling power and low vibrations.

background

As known, the technologies that use rotary valve or piston or displacer systems are widely used in various fields of industry and scientific research. An example are the cryogenic systems based on the use of closed-cycle cryo-refrigerator machines, which use the expansion of a fluid, typically gaseous helium, to generate cooling power. These cryo-refrigerating machines find particular application in all those fields, scientific and industrial, in which required to reach a temperature below 100-120 K with a high cooling power and/or a low level of vibrations. For example, in the field of quantum computers, or calculators that exploit the laws of physics and quantum mechanics, whose operation requires very low temperatures, close to absolute zero (about -273? C),? It is necessary to prepare environments with low temperatures, high cooling capacity and low vibrations. Why? quantum computers often use a series of pulsed tube cryocoolers or ?Pulse Tube Cryocoolers? (PTC) as pre-coolers or ?precoolers? integrated in multistage cryogenic systems, typically so-called dilution cryostats, that is? cryogenic devices that reach temperatures below fractions of a degree Kelvin, continuously.

Compared to other closed cycle cryocoolers, due to the absence of low temperature moving parts, PTCs have the advantage of providing a lower level of vibration. low, at the expense of a pi? modest cooling power. For this reason ? common practice to equip the same cryogenic system with more? of a PTC when you want to have a high cooling power without giving up a low level of vibrations.

In addition to quantum computers, there are numerous other industrial applications in which PTCs, and more in general, closed-cycle cryocoolers are widely used, such as:

? ?precooler? for dilution cryostats;

? coolers for liquefaction plants for gases or gas compounds (nitrogen, helium, air, etc.);

? cryogenic pumps, i.e. gas capture cryopumps in which the gaseous substances bind to the cold surfaces inside the pump and which are used to produce high vacuum in the chambers used, for example, for the manufacture of semiconductor products;

? military applications such as infrared sensor cooling, where thermal imaging cameras are cooled to reduce thermal noise;

? SQUID magnetometers (Superconducting Quantum Interference Devices), or superconducting quantum interference devices, which are extremely sensitive instruments, used to measure very weak magnetic fields, in health and medical applications.

Closed-cycle cryocoolers are also particularly useful in space telescopes, such as the James Webb Space Telescope, which will reach the Hubble Space Observatory in space and where it won't be? It is possible to replenish the cryogens as they run out, or in space exploration, such as in future missions to Mars, where they could be used to liquefy oxygen on the planet's surface.

Finally, numerous other uses of closed-cycle cryocoolers, and in particular of PTCs, in the scientific field can be listed, including:

? tunneling effect microscopy;

? cold optical systems;

? low-energy physics experiments and rare events, such as, for example, the CUORE experiment (Cryogenic Undregroung Observatory for Rare Events) currently in operation at the underground headquarters of the Gran Sasso National Laboratories;

? particle accelerators and facilities for high energy physics (CERN, etc.);

? interferometry for the search for gravitational waves (eg, KAGRA, Einstein Telescope);

? astronomical detectors (eg, the Atacama cosmological telescope, the Qubic experiment).

In all these applications ? required a high cooling power and a low level of vibrations.

By way of example, the present invention refers to cryogenic systems which contain at least two pulsed tube cryocoolers (PTC) of the Gifford-McMahon type (GM-type). However, the present invention is not limited only to PTC GM-type, but ? also applicable to PTCs of different types (for example PTC Stiling-type), to Stirling machines, and to Gifford McMahon type chillers. Pi? in general, the following invention is not? limited to cryogenic systems only, but refers in general to all those systems which produce vibrations and which include means for the production of pressure oscillations, such as e.g. rotary valves, pistons, displacers, which are operated simultaneously.

The main responsible for the production of vibrations within the cryogenic systems that use, for example, the GM-type PTCs, and in general within all the systems that use more? means for producing pressure oscillations in a simultaneous manner, are the motors which drive said means. For example, in a cryogenic system equipped with pi? of a GM-type PTC, each single rotary valve belonging to each PTC is operated individually and independently of the others. Consequently each PTC works at its own operating frequency defined around a characteristic value (typically around a few Hz), unless the precision is defined by the drive device used. When a certain number of PTCs are operated simultaneously and in a non-synchronized manner, forced vibrations of different and close frequencies are produced in the cryogenic system, due to the phase shift of the forcers, which, when superimposed, give rise to beats within the system. Because of this, the noise power spectrum of the system will contain components of variable amplitude over time, which inevitably make the filtering and signal extraction operations ineffective. Furthermore, among all the possible configurations of phase shift between the different PTCs installed in the system, will there be any? at least one that optimizes certain variables/parameters of the system, such as the level of vibrations and the cooling capacity.

In general there are several approaches to mitigate the vibration problem in low temperature systems. Basically they can be grouped into two categories, both at room temperature and at cryogenic temperature:

? passive countermeasures, including shock absorbers, decouplers, bellows, spring systems, remote PTC rotary valve drives, remote PTC controls;

? active countermeasures, including electronic shock absorbers or actuators.

For example, in the American patent US 10,162,023 B2, belonging to Oxford Instruments, a noise reduction apparatus is presented in a pulsed tube cooler, which finds particular application in magnetic resonance imaging systems. The apparatus consists of a dispersion chamber in which the pressure waves coming from the PTC are directed and divided. The apparatus acts on the pressure waves caused by a single PTC and disperses them thanks to its specific architecture, but it is not? usable in the event that the vibrations are generated by the motion of pi? mechanical parts in conflict, such as, for example, a system consisting of more? of a PTC.

For example, in US Patent 8,639,388 B2 belonging to the Raytheon Company, a system for "Adaptive phase control for active cryocooler vibration cancellation" is presented, which applies a canceling force (via an actuator) to the vibrations of the PTC and a sensor to adjust the oscillations to be out of phase and destructively interfering. This system uses vibrations generated by pressure waves from a single PTC, vibrations that destructively interfere with those produced by a mechanical actuator, but again, a second PTC is not used for interference.

Ultimately, the solutions adopted so far to address the problem of vibrations in ?cryogen-free? Are they essentially based on hardware modification? of the architecture of the PTC or of the cryogenic infrastructure, but they have the disadvantage of reducing the cooling power produced and/or increasing the complexity? of the system. In addition to being quite invasive, most of the existing solutions also act as mere passive countermeasures. Finally, none of the known countermeasures acts on systems operating two or more? cryocoolers simultaneously.

Therefore, it is necessary to develop a device and a method which allow the substantial reduction of the vibration level in systems comprising several? means for producing pressure oscillations that can be operated simultaneously, such as cryogenic systems comprising at least two PTC cryocoolers, without having to resort to substantial modifications of the cryocooler infrastructure, or to introduce additional thermodynamic and/or mechanical components within the cryogenic system itself.

Summary

Object of the present invention ? a method and a device for synchronizing the engines which operate the means for producing pressure oscillations (for example rotary valves, pistons or displacers) within a system comprising at least two identical means or a combination thereof of them.

According to an embodiment of the claimed method, there is provided a single device configured to synchronize the operation of the motors driving said means for producing pressure oscillations, contained within said system, said motors being all operated at exactly the same frequency.

According to one embodiment, said device or ?drive? of motor drive, ? a unique power converter, custom designed and optimized for controlling the actuation of the motors driving said means for producing pressure swings, in a system comprising at least two of said means, in a synchronized and coordinated manner.

According to a particular embodiment, said system ? a cryogenic system formed by at least two Stirling-type cryocoolers, and said means for producing pressure oscillations are piston/displacer pairs, each pair being associated with its own Stirling cryocooler.

According to a different embodiment, said system ? a cryogenic system formed by at least two Gifford-Mc Mahon (GM) type cryocoolers, and said means for producing pressure oscillations are rotary valve/displacer pairs, each pair being associated with a compressor included in its own GM cryocooler.

According to another embodiment, said system ? a cryogenic system formed by at least two Stirling-type pulsed tube cryocoolers (PTC Styrlingtype), and said means for producing pressure oscillations are pistons, each piston being associated with its own PTC Styrling-type cryocooler.

According to a further embodiment, said system ? a cryogenic system formed by at least two pulsed tube cryocoolers of the Gifford-McMahon type (PTC GM-type), and said means for producing pressure oscillations are rotary valves, each pair being associated with a compressor included in its own PTC GM- type.

According to a preferred embodiment, the claimed method allows to reduce the level of vibrational noise, produced inside a cryogenic system, comprising at least two GM-type PTC cryo-coolers, by the overlapping of the operating frequencies of each of said at least two GM-type PTC cryocoolers, by synchronizing the operation of the motors driving the rotary valves of said at least two PTC cryocoolers. The movement of each rotary valve of each PTC originates pressure oscillations which are the basis of both the cooling power of the PTC and the generation of its characteristic noise.

According to one embodiment, the proposed method uses a single device or ?drive? of motors actuation, said device being a power converter for operating all the rotary valves ? each contained within each PTC - simultaneously and based on a common sync signal. The proposed device is also able to reduce the vibrational noise level, managing the relative movement of each rotary valve and making them rotate simultaneously at the same frequency. According to a further embodiment, the claimed method uses the characteristic noise produced by each of the individual at least two GM-type PTCs to create destructive interference, exploiting the coherent superimposition of the mechanical vibrations generated by the pressure waves in order to obtain noise cancellation . According to a further embodiment, the claimed method uses the characteristic working frequency of each of the single at least two GM-type PTCs to exploit the coherent overlapping of the oscillations in order to obtain the maximization of the cooling power of the system.

A previous customer project called "Active Pulse Tube Noise Cancellation" (APTNC), provided a first validation of the effectiveness of the noise cancellation technique both in experimental physics (D?Addabbo et al., ?An active noise cancellation technique for the CUORE Pulse Tube Cryocoolers?, Cryogenics, 93:56?65, May 2018; V. Domp? et al.; ?The CUORE Pulse Tube Noise Cancellation Technique?; J. Low Temp. Phys., https://doi. org/10.1007/s10909-020-02435-0, Mar 2020) that in the relevant industrial environments, through the development of a software that drives two or more? ?drive? commercial grade linear motor drives. The two cited articles concern the results obtained by applying the active noise cancellation technique in the CUORE experiment, which uses a cryostat operating up to five GM-type PTCs simultaneously.

The methodology object of the present invention, although using the same technique, presents three elements of innovation compared to the previous APTNC project:

1. the use of a single motor drive device (or ?drive?) for the entire cryogenic system, instead of one ?drive? for each cryo-cooler PTC or similar; 2. the development of a device, custom designed and optimized for the operations of the media responsible for the pressure oscillations (such as rotary valves, pistons and displacers) of PTC or similar cryo-coolers, rather than? the use of ?drive? commercial linears manufactured for different purposes;

3. the implementation of a method based on the synchronization of the operations of the means responsible for the pressure oscillations (such as rotary valves, pistons and displacers) by means of a common synchronization signal, instead of? the use of methods based on the continuous regulation of the speed? of said means (as implemented in the APTNC project and in the CUORE experiment).

The technology object of the present invention represents a further step forward with respect to previous technologies. In fact, the use of ?drive? commercial linear low noise to operate said means (such as the rotary valves of GM-type PTCs) ? already known in the industrial field, but this use ? limited in the 1:1 ratio (i.e. a linear "drive" for actuating a single means for the production of pressure oscillations) and for the sole purpose of passively reducing the electromagnetic noise and radio frequency interference generated by the drive of the same and from the operating environment. By way of example, the use of said ?drive? low noise linear ? was adopted for the activation of the rotary valves installed on the five GM-type PTCs manufactured by the Cryomech company and installed in the CUORE experiment.

To greater advantage, said device ? compatible with PTC GM-type products from various companies, such as, for example, the gi? mentioned Cryomech, or the Sumitomo company, which produce GM-type PTCs equipped with rotary valves with different types of motor drive. Furthermore, the device provided by the present invention ? compatible and integrable with all types of ?cryogen-free? closed-loop systems on the market, and ? finally backwards compatible with ?cryogenfree? already in operation, being able to be added, and made operational, after the implementation of the system.

The device object of the present invention ? equipped with management software that interfaces with the system user. According to a preferred embodiment said software ? equipped with a graphical interface and a series of algorithms, through the implementation of which? Active noise cancellation can be obtained in a system comprising a number of GM-type PCTs equal to at least two units.

According to a different embodiment, said software allows to use a series of algorithms to obtain the maximization of the cooling power of the system comprising a number of GM-type PCTs equal to at least two units.

According to a further embodiment, said software ? it can also be implemented in systems comprising a number of GM-type PTCs between two and four units.

According to a further embodiment, said software ? implementable in systems comprising a number of ?cryogen-free? closed loop (including PTC) greater than or equal to two units?.

Brief description of the figures

- Fig.1. Operation diagram of a closed cycle cryo-cooler according to the prior art.

- Fig.2. Schematic representation of a motor control device operating N?2 rotary valves within a cryogenic system consisting of N?2 Pulsed Tube (PTC) cryocoolers according to an embodiment of the present invention.

- Fig.3. Block diagram of a device designed to control the motors which operate N?2 rotary valves of a cryogenic system according to the present invention.

Detailed description

Described below is a method and device for controlling motors which operate means for producing pressure oscillations (such as, for example: rotary valves, pistons, displacers) within a system comprising at least two of said means.

In particular, the proposed method is particularly effective for the reduction of the mechanical vibrational noise and/or for the maximization of the refrigerating power generated within a cryogenic system consisting of at least two closed-cycle cryo-coolers, each of said cryo-coolers equipped with at least one of the said means for the production of pressure oscillations, and applicable in all those environments in which ? required a high vacuum and/or cooling capacity and a low vibrational level.

Alternately combinations of compressors and/or pistons/displacers working at high frequencies (typically 25-400 Hz), or combinations of compressors and rotary valves/displacers working at higher frequencies can be used to produce the pressure oscillations. low (typically 0.5-5 Hz).

For example, in Stirling cryo-coolers (Fig.1A), the pressure oscillations are generated by the movement of one or more? pistons (10A) directly connected with a chamber (11A), coordinated with the movement of a displacer (12A) arranged inside it, and controlled by a motor (not shown in the figure).

In another example, in cryo-coolers of the Gifford-McMahon type (Fig.1B), the pressure oscillations are generated by a compressor (13B) associated with a rotary valve (14B) directly connected to a chamber (11B), coordinated with the movement of a displacer (12B) arranged inside it, and controlled by a motor (not shown in the figure).

The pulsed tube cryo-coolers or ?Pulse Tube Cryocooler? (PTC) act in a completely analogous way to the previous ones, with the difference that the role of the displacer (12A, 12B) ? played by the gas itself which moves back and forth in the so-called ?pulsed tube?.

So for example, in Stirling-type Pulse Tube cryo-coolers (Stirling-type PTC), Fig.1C, the pressure oscillations are generated by the movement of one or more? pistons (10C) directly connected with the pulsed tube (15C) and controlled by a motor.

While, for example, in Gifford-McMahon type Pulse Tube cryo-refrigerators (GM-type PTC), Fig.1D, the pressure oscillations are generated by a compressor (13D) associated with a rotary valve (14D) directly connected with the tube pulsed (15D) and controlled by a motor.

As mentioned, the proposed method pu? be applied to any of the types of closed cycle cryo-coolers among those listed, aimed at reducing vibrational noise and/or maximizing the cooling power.

The proposed method is particularly effective for the reduction of the mechanical vibrational noise created within a cryogenic system consisting of at least two closed-cycle GM-type pulsed tube cryo-coolers (PCT) (PTC GM-type).

A pulse tube cryocooler, or Pulse Tube cryocooler (PTC), ? a fluid machine for the production of cold, in particular of cryogenic temperatures below ~120 K, whose cooling power is ? supplied by expansion/compression cycles of the fluid evolving in it, normally helium pressurized at a few tens of bars, obtained by means of a high-frequency pressure oscillation generator (as in a ?Stirling? cooler (Fig.1C), for example through a piston of expansion/compression) or through a compressor to pi? low frequency associated with a rotary valve (such as in a ?Gifford-McMahon chiller, Fig,1D). For this reason the PTCs of the first type are also called ?Stirling-type? PTC, while those of the second type are also called ?GM-type? PTC extension.

The cooling effect is based on a periodic variation of the pressure within one or more? thin-walled tubes (15C, 15D) with heat exchangers (17C, 17D, 18C, 18D) at both ends? and connected to a regenerator (16C, 16D) of large capacity? thermal.

As shown in Fig.1C and Fig.1D , the thin hollow cylindrical tube (15C, 15D), or pulsed tube, ? placed between the ?hot exchanger? (17C, 17D), which transfers the heat accumulated during the cycle to the outside, and the exchanger is cold (18C, 18D), placed in contact with the body to be refrigerated, and is? connected with regenerative material (16C, 16D), such as metal meshes or granules (e.g. stainless steel, bronze, brass, copper, lead or rare earths). For example, in GM-type PTCs (Fig.1D) the pressure cycles are generated by a rotary valve (14D) positioned inside the motor head at room temperature of the PTC. Said rotary valve typically makes between 0.5 and 5 revolutions per second and alternately connects the PTC to the high and low pressure side of a compressor (13D). There? it results in pressure waves with a frequency that depends on the model of the PTC used.

The variations of the thermodynamic parameters of the gas provide the cooling power (or refrigerating power), but they are also a source of mechanical noise at the frequency of the rotary valve and its harmonics.

The rotary valves used in modern PTCs are driven by motors which may require different types of power supplies, depending on the model chosen.

According to an embodiment of the invention, as shown in Fig.2, the claimed method provides a device (20) which allows to synchronize the rotational movement of two or more? rotary valves (21), each serving a different GM-type PTC, so that they operate at exactly the same frequency.

The device (20) supplied according to the invention, or ?drive? engine drive, acts on? the whole system and ? designed to adapt to different systems comprising at least two means for generating pressure oscillations, arranged in two different independent machines (such as for example two rotary valves, or two pistons, or two pairs of valves/displacers, or two pairs of valves/pistons, in a system composed of two closed cycle cryocoolers); for example, can be used in a cryogenic system (200) composed of two or more? GM-type PTC cryo-coolers, to simultaneously control the motors that operate the rotary valves (21) contained in each of the PTCs (one rotary valve for each PTC). The device ? customizable according to the system in which it must operate and pu? be tailored to, for example, the model of PTC cryocoolers it is to operate. By way of example, in the case of the GM-type PTC cryo-coolers marketed by one of the leading companies in the sector, the motors that operate the rotary valves are stepper motors fed with a pair of square waves, in phase quadrature with each other, of fixed amplitude and frequency proportional to the rotation frequency of the valve.

Again by way of example, in the case of GM-type PTC cryocoolers marketed by another company, the motors that operate the rotary valves are synchronous or asynchronous motors fed with a triad of sine waves, phase-shifted by an angle of 120?, of fixed amplitude and frequency proportional to the rotation frequency of the valve.

Normally in a cryogenic system each rotary valve ? powered by its own motor. In a cryogenic system consisting of two or more? PTC, each rotary valve is operated by a motor supplied with a set of waveforms, in number, shape, amplitude and frequency typical of the PTC model in use. The difference in the operating frequency of several groups of waveforms, each driving an independent rotary valve and belonging to an independent PTC, generates a progressive phase shift between the operating frequencies of the different PTCs. This phase shift? at the origin of the forced vibrations of different and close frequencies which are at the basis of the generation of the beats and therefore of the changing noise of the system.

According to an embodiment of the claimed method each of the motors involved in the cryogenic apparatus is fed with a set (for example with a pair or with a triad) of waveforms of the same origin and of the same frequency, which therefore remain unchanged in the time their mutual phase difference. The frequency of each pair or triad of waveforms? modifiable independently of the others, in order to find the reciprocal phase configuration between the pressure oscillations generated by the different cryocoolers involved in the system, which minimizes the system noise and/or which maximizes the system's cooling capacity. According to a preferred embodiment, as shown in Fig.2, the device (20) provided according to the claimed method ? configured to handle a plurality? of rotary valves (21) and comprises a plurality? of electronic cards, each electronic card being associated with one or more? several rotary valves (21); a first electronic card of said plurality? of boards acts as ?master?, while the remaining electronic boards act as ?slave?, each having its own drive. Said first electronic card, acting as ?master?, manages the operations of said ?slave? via a microcontroller whose sequence of instructions is programmed with an integrated software, or ?firmware? low-level, which operates at the pi? high frequency compared to the movement of the valves. Said first electronic card, acting as "master" also supplies the synchronization signal for said "slave" cards.

According to an embodiment of the device provided with the present invention (Fig.3), the hardware architecture (300) of said device (20) comprises a power converter (30), the diagnostics and control of which are also managed from the same ?firmware?. Said power converter (30) includes one or more? power boards (32), or ?Power Boards?, responsible for the electrical transformation of the wave form arriving from the network (33), and from one or more? control boards (34), or ?Control Board?, which manage a conditioning network of switches (35) belonging to the ?Power Board? (32) and subservient to it. According to one embodiment, called the ?master? (34A), via a microcontroller (35A) also takes care of the management of the peripherals and communication protocols and of the interface with the outside world. According to a further embodiment, a second microcontroller (35B) manages the peripherals and communication protocols and interfaces with the outside world via a second ?firmware? more high level. In particular, said interface ? arranged to receive commands from a software (36) for the control and management of the user interface and to send readings to said software (36), of which the undersigned has all the rights, according to a communication protocol, which is defined on the basis to the needs? of performance and speed? of the device.

According to an embodiment of said software (36), the interface ? arranged for communication with a number of pressure sensors (37) equal to the number of cryocoolers involved in the system, each installed in communication with the chamber in which the pressure oscillations are produced which are the basis of the generation of the cooling power and the characteristic noise.

According to an embodiment of said software (36), the interface ? set up for communication with a number of vibration sensors (37) (for example accelerometers, geophones, etc.) equal to the number of geometric axes (Cartesian) involved in the system, each installed in direct mechanical contact with the chamber in which it is desired minimize characteristic noise.

According to an embodiment of said software (36), the interface ? set up for communication with any number of temperature sensors (37), installed in direct thermal contact with the chamber in which the cooling power is to be maximized.

According to an embodiment of said software, the interface ? arranged for communication with the device firmware/s in order to modify the relative phase between the means responsible for generating the pressure oscillations (38) belonging to different cryocoolers but installed on the same system. The phase configuration chosen? identified through an indexer integrated into the device, and ? which can be associated with a real phase configuration of the system through the readings provided by the pressure sensors. Thanks to a software algorithm ? It is possible to map the entire space of possible phase configurations, and prepare noise and/or temperature readings to be associated with each specific configuration. In this way ? possible to identify, identify, select and maintain over time the specific phase configuration that minimizes noise or maximizes the cooling power.

According to the preferred embodiment of the invention, the software for controlling and managing the user interface (36), as well as all the operations necessary for minimizing the noise and/or maximizing the cooling power, ? configured for a cryogenic system composed of at least two PTCs. According to another embodiment, said software (36) ? configured to operate with a cryogenic system consisting of between two and four PTC units. According to a further embodiment said software (36) ? configured to operate with a cryogenic system composed of a number of cryocoolers greater than or equal to two units.

Finally, it is clear that modifications and variations can be made to what is described and illustrated herein without thereby departing from the scope of protection of the present invention, as defined in the attached claims.

In particular, it is reiterated that the means for producing pressure oscillations (38) can be not only rotary valves, but also pistons, displacers, or any other means actuated by a motor controllable by the proposed device, according to the proposed method. Furthermore, it is emphasized again that the number of rotary valves (or any other type of means for the production of pressure oscillations) that can? be managed through the proposed method pu? vary from what was previously illustrated, and the aforementioned method pu? be applied for the control of the engines that operate said means in a system that also has finality? different from those illustrated in the present description, but which is composed of a number of said means at least equal to two.

Claims (11)

1. Device (20, 300) for controlling the motors which drive the means for producing pressure oscillations (38) in a system which produces vibrations, said system comprising at least two means for producing pressure oscillations (38) , said device being a ?drive? for motor drive (300), custom designed and optimized for synchronously driving said motors driving said at least two means for producing pressure swings (38). 2. Device (20, 300) according to claim 1, characterized in that it comprises: - a first electronic board (34A) acting as ?master? and at least one second electronic card (34B) acting as a "slave", said first electronic card (34A) being configured to manage and coordinate the operations of said first and said at least one second electronic card (34A, 34B), said first and said at least a second electronic board (34A, 34B) being associated with said at least two means for producing pressure oscillations (38); - management and user interface software (36) for controlling and managing all the operations aimed at synchronizing the operations of said at least two means for producing pressure oscillations (38); - an interface configured to receive commands from the management software (36) and send readings to the management software (36) according to a communication protocol commensurate with the needs? of performance and speed? of said device. 3. Device (20, 300) according to claim 2, wherein said first electronic board (34A) supplies the synchronization signal through at least one microcontroller (35A) programmed by means of a ?firmware? configured to perform tasks? low-level, said microcontroller (35A) operating at frequency pi? high with respect to the motor drive signals provided by said device (20, 300) to said at least two means for producing pressure oscillations (38). 4. Device (20, 300) according to claim 1, wherein said system which produces vibrations ? a cryogenic system (200) formed by at least two cryo-coolers, said at least two cryo-coolers comprising at least two means for producing pressure oscillations (38), said means (38) comprising rotary valves (14B, 14D), pistons (10A, 10C), displacers (12A, 12B) or combinations thereof. 5. Device (20, 300) according to claim 4 characterized by the fact that it is compatible and can be integrated with all types of cryo-coolers, said types comprising closed-cycle cryo-coolers of the Stirling type, Gifford Mc-Mahon type and pulsed tube type (PTC). 6. Method for synchronizing the motors which operate the means for producing pressure oscillations (38) in systems comprising at least two of said means (38), characterized in that it provides a device or ?drive? of motor drive (20, 300) custom designed and optimized for synchronizing the actuation of the motors driving said at least two means for producing pressure oscillations (38). 7. Method according to claim 6, wherein said device (20, 300) is a power converter (30) configured to operate said at least two means for producing pressure oscillations (38) simultaneously by emitting a common synchronization signal. 8. A method according to claim 6 wherein said vibration producing system ? a cryogenic system (200) formed by at least two cryocoolers, said at least two cryocoolers comprising at least two means for producing pressure oscillations (38), said means (38) comprising rotary valves (14B, 14D), pistons (10A , 10C), displacers (12A, 12B) or combinations thereof. 9. Method according to claim 8, characterized in that it uses the characteristic noise of each of said at least two cryo-coolers to create destructive interferences, exploiting the coherent superimposition of the mechanical vibrations generated by the pressure oscillations in order to obtain the minimization or cancellation of system noise together. 10. Method according to claim 8, characterized in that it uses the characteristic working frequency of said at least two cryo-coolers to create interferences, through the coherent superposition of the pressure oscillations in order to obtain the maximization of the cooling power of the system. 11. Method according to any one of claims 8? 9 - 10 in which said device supplied ? compatible and integrable with all types of cryo-chillers, these types including closed-cycle cryo-chillers of the Stirling, Gifford Mc-Mahon and pulsed tube type (PTC) types.